1-Thiadiazolyl-6-acyloxytetrahydropyrimidinone herbicides

ABSTRACT

Disclosed are new compounds of the formula   &lt;IMAGE&gt;   wherein R1 is selected from the group consisting of alkyl, alkenyl, haloalkyl, alkoxy, alkylthio, alkylsulfonyl and alkylsulfinyl; R2 is selected from the group consisting of alkyl, alkenyl, haloalkyl and   &lt;IMAGE&gt; wherein R3 and R4 are each selected from the group consisting of hydrogen and alkyl; and R5 is selected from the group consisting of alkyl, haloalkyl, alkenyl, alkynyl, alkoxyalkyl, cycloalkyl and &lt;IMAGE&gt;  WHEREIN X is selected from the group consisting of alkyl, halogen, haloalkyl, nitro, cyano and alkoxy, and m and n are each integers from 0 to 3. The subject compounds are useful as herbicides.

This invention relates to new compositions of matter and morespecifically relates to new chemical compounds of the formula ##STR4##wherein R¹ is selected from the group consisting of alkyl, alkenyl,haloalkyl, alkoxy, alkylthio, alkylsulfonyl and alkylsulfinyl; R² isselected from the group consisting of alkyl, alkenyl, haloalkyl and##STR5## wherein R³ and R⁴ are each selected from the group consistingof hydrogen and alkyl; and R⁵ is selected from the group consisting ofalkyl, haloalkyl, alkenyl, alkynyl, alkoxyalkyl, cycloalkyl and ##STR6##WHEREIN X is selected from the group consisting of alkyl, halogen,haloalkyl, nitro, cyano and alkoxy, and m and n are each integers from 0to 3.

In a preferred embodiment of the present invention R¹ is selected fromthe group consisting of lower alkyl, lower alkenyl, lower chloroalkyl,lower bromoalkyl, trifluoromethyl, lower alkoxy, lower alkylthio, loweralkylsulfonyl and lower alkylsulfinyl; R² is selected from the groupconsisting of lower alkyl, lower alkenyl, lower chloroalkyl, lowerbromoalkyl and ##STR7## wherein R³ and R⁴ are each selected from thegroup consisting of hydrogen and lower alkyl; and R⁵ is selected fromthe group consisting of lower alkyl, lower chloroalkyl, lowerbromoalkyl, lower alkenyl, lower alkynyl, lower alkoxyalkyl, cycloalkylof from 3 to 7 carbon atoms and ##STR8## wherein X is selected from thegroup consisting of lower alkyl, lower alkoxy, halogen and lowerhaloalkyl, and m and n are each integers from 0 to 3.

The term "lower" as used herein designates a straight or branched carbonchain of up to six carbon atoms.

The compounds of the present invention are unexpectedly useful asherbicides.

The compounds of this invention can be prepared by reacting a compoundof the formula ##STR9## wherein R¹ and R² are as heretofore described,with an acid anhydride of the formula ##STR10## wherein R⁵ is asheretofore described, in the presence of a catalytic amount oftoluenesulfonic acid. This reaction can be effected by combining thereactants and the catalyst at room temperature in an inert organicreaction medium and then heating the reaction mixture on a steam bath ata temperature of from 50° to 90° C with stirring for a period of from1/2 to 4 hours. After this time the reaction mixture can be cooled andthe desired product can be recovered by filtration if formed as aprecipitate or upon evaporation of the organic reaction medium ifsoluble therein. In some instances the acid anhydride can be used as asolvent for the compound of formula II, obviating the use of an inertsolvent as the reaction medium. When lower alkanoic anhydrides are used,water can be added to the reaction mixture to precipitate the desiredproduct upon completion of the reaction. The product can then bepurified by conventional means such as recrystallization and the like.

The compound of this invention can also be prepared by reacting thecompound of formula II with an acid halide of the formula ##STR11##wherein R⁵ is as heretofore described, in the presence of an acidacceptor such as a tertiary amine. The preparational method can beutilized when the desired anhydride of formula III is not available.This reaction can be effected by slowly adding the acid chloride offormula IV, with stirring, to a solution of an about equimolar amount ofthe compound of formula II in an inert organic solvent, in the presenceof an acid acceptor, at a temperature of about 10° to 30° C. After theaddition is completed, the reaction mixture can be heated at atemperature ranging up to the reflux temperature of the mixture toensure completion of the reaction. The desired product can then berecovered by first filtering the reaction mixture to remove acidacceptor chloride, followed by stripping off the solvent if the productis soluble therein, or, if formed as a precipitate, by filtration andsubsequent washing and purification.

The compounds of formula II can be prepared by heating a compound of theformula ##STR12## wherein R¹ and R² are as heretofore described and R⁶and R⁷ are methyl or ethyl, in a dilute, aqueous, acidic reaction mediumfor a period of about 10 to about 60 minutes. Temperatures of from about70° C to the reflux temperature of the reaction mixture can be utilized.The reaction medium can comprise a dilute aqueous inorganic acid such ashydrochloric acid at a concentration of from about 0.5 to about 5percent. Upon completion of the reaction the desired product can berecovered as a precipitate by cooling the reaction mixture. This productcan be used as such or can be further purified by conventional meanssuch as recrystallization and the like.

The compounds of formula IV can be prepared by reacting a molar amountof an isocyanate dimer of the formula ##STR13## wherein R¹ is asheretofore described, with about two molar amounts of an acetal of theformula ##STR14## wherein R², R⁶ and R⁷ are as heretofore described.This reaction can be effected by heating a mixture of the isocyanatedimer and the acetal in an inert organic reaction medium such as benzeneat the reflux temperature of the reaction mixture. Heating at reflux canbe continued for a period of from about 2 to about 30 minutes to ensurecompletion of the reaction. After this time the desired product can berecovered upon evaporation of the reaction medium and can be used assuch or can be further purified by standard techniques in the art.

The isocyanate dimer of formula VI can be prepared by reacting athiadiazole of the formula ##STR15## wherein R¹ is as heretoforedescribed, with phosgene. This reaction can be effected by adding aslurry or solution of the thiadiazole, in a suitable organic solventsuch as ethyl acetate, to a saturated solution of phosgene in an organicsolvent such as ethyl acetate. The resulting mixture can be stirred atambient temperatures for a period of from about 4 to about 24 hours. Thereaction mixture can then be purged with nitrogen gas to removeunreacted phosgene. The desired product can then be recovered byfiltration if formed as a precipitate or upon evaporation of the organicsolvent used if soluble therein. This product can be used as such or canbe further purified if desired.

Exemplary thiadiazoles of formula VIII useful for preparing thecompounds of the present invention are5-methyl-2-amino-1,3,4-thiadiazole, 5-ethyl-2-amino-1,3,4-thiadiazole,5-propyl-2-amino-1,3,4-thiadiazole, 5-allyl-2-amino-1,3,4-thiadiazole,5-pent-3-enyl-2-amino-1,3,4-thiadiazole,5-chloromethyl-2-amino-1,3,4-thiadiazole,5-β-chloroethyl-2-amino-1,3,4-thiadiazole, 5-γ-chloropropyl-2-amino-1,3,4-thiadiazole,5-trichloromethyl-2-amino-1,3,4-thiadiazole,5-methoxy-2-amino-1,3,4-thiadiazole, 5-ethoxy-2-amino-1,3,4-thiadiazole,5-propoxy-2-amino-1,3,4-thiadiazole,5-butyloxy-2-amino-1,3,4-thiadiazole,5-hexyloxy-2-amino-1,3,4-thiadiazole,5-methylthio-2-amino-1,3,4-thiadiazole,5-ethylthio-2-amino-1,3,4-thiadiazole,5-propylthio-2-amino-1,3,4-thiadiazole,5-butylthio-2-amino-1,3,4-thiadiazole,5-methylsulfonyl-2-amino-1,3,4-thiadiazole,5-ethylsulfonyl-2-amino-1,3,4-thiadiazole,5-butylsulfonyl-2-amino-1,3,4-thiadiazole,5-methylsulfinyl-2-amino-1,3,4-thiadiazole,5-ethylsulfinyl-2-amino-1,3,4-thiadiazole,5-propylsulfinyl-2-amino-1,3,4-thiadiazole,5-t-butyl-2-amino-1,3,4-thiadiazole,5-trifluoro-methyl-2-amino-1,3,4-thiadiazole and the like.

The acetal of formula VII when not readily available can be prepared byreacting an amine of the formula ##STR16## wherein R² is as heretoforedescribed with the dimethyl or diethyl acetal of β-bromopropionaldehyde.This reaction can be effected by combining from about 1 to about 2 molaramounts of the amine of formula IX with one molar amount of the acetalof β-bromopropionaldehyde in about equimolar proportions in an inertorganic reaction medium such as methanol. The reaction mixture can thenbe heated at reflux for a period of from about 4 to about 8 hours. Afterthis time the reaction mixture can be cooled to room temperature and analkali metal hydroxide or carbonate can be added in an amount sufficientto neutralize the reaction mixture. Stirring can be continued at roomtemperature for a period of up to about 24 hours to ensure completion ofthe reaction. After this time the reaction mixture can be filtered andthe filtrate distilled under reduced pressure to yield the desiredproduct.

Exemplary compounds of formula IX are methylamine, ethylamine,propylamine, isopropylamine, n-butylamine, t-butylamine, pentylamine,hexylamine, allylamine, propargylamine, 2-butenylamine, 3-butenylamine,3-pentenylamine, 4-pentenylamine, 5-hexenylamine,1-methyl-2-propynylamine, 1,1-dimethyl-2-propynylamine,1-ethyl-2-propynylamine, 1,1-diethyl-2-propynylamine,1-propyl-2-propynylamine, 1,1-dipropyl-2-propynylamine,1-chloroallylamine, 1-bromoallylamine, 4-chloro-2-butenylamine,6-chloro-4-hexenylamine and the like.

Exemplary suitable acid anhydrides of formula III are acetic anhydride,propionic anhydride, butanoic anhydride, pentanoic anhydride, hexanoicanhydride, acrylic anhydride, butenoic anhydride, pentenoic anhydride,chloroacetic anhydride, bromoacetic anhydride, β-chlorobutanoicanhydride, cyclohexylcarboxylic anhydride, benzoic anhydride, toluicanhydride, 4-chlorobenzoic anhydride, 3-bromobenzoic anhydride,4-fluorobenzoic anhydride, 4-methoxybenzoic anhydride, 4-ethoxybenzoicanhydride, 4-chloromethylbenzoic anhydride, 4-trifluoromethylbenzoicanhydride, 3,4,5-trichlorobenzoic anhydride, phenylacetic anhydride,4-methylphenylacetic anhydride, β-phenylpropionic anhydride,γ-phenylbutanoic anhydride, propynoic anhydride, butynoic anhydride,methoxyacetic anhydride, β-methoxypropionic anhydride, γ-ethoxybutanoicanhydride and the like.

Exemplary suitable acid chlorides of formula IV useful for preparing thecompounds of the present invention are the acid halides of the sameacids as set forth above in the examples of acid anhydrides.

The manner in which the compounds of the present invention can beprepared is more specifically illustrated in the following examples.

EXAMPLE 1 Preparation of 5-Methyl-1,3,4-thiadiazol-2-yl Isocyanate Dimer

A saturated solution of phosgene in ethyl acetate (100 ml) is chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-methyl-2-amino-1,3,4-thiadiazole (40 grams) in ethyl acetate(300 ml) is added to the reaction vessel and the resulting mixture isstirred for a period of about 16 hours, resulting in the formation of aprecipitate. The reaction mixture is then purged with nitrogen gas toremove unreacted phosgene. The purged mixture is then filtered torecover the precipitate. The precipitate is then recrystallized to yieldthe desired product 5-methyl-1,3,4-thiadiazol-2-yl isocyanate dimer.

EXAMPLE 2 Preparation of the Dimethyl Acetal of3-Methylaminopropionaldehyde

Methylamine (1.0 mole), the dimethyl acetal of 3-bromopropionaldehyde(0.5 mole) and methanol (100 ml) are charged into a glass reactionvessel equipped with a mechanical stirrer, thermometer and refluxcondenser. The reaction mixture is heated at reflux, with stirring, fora period of about 4 hours. After this time the reaction mixture iscooled to room temperature and sodium hydroxide (20 grams) is added. Thereaction mixture is then stirred for an additional period of about 8hours. The reaction mixture is then filtered and the filtrate isdistilled under reduced pressure to yield the desired product thedimethyl acetal of 3-methylaminopropionaldehyde.

EXAMPLE 3 Preparation of the Dimethyl Acetal of3-[1-Methyl-3-(5-methyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-methyl-1,3,4-thiadiazol-2-yl isocyanate dimer (0.05mole), the dimethyl acetal of 3-methylaminopropionaldehyde (0.1 mole)and benzene (60 ml) are charged into a glass reaction vessel equippedwith a mechanical stirrer and reflux condenser. The reaction mixture isheated at reflux for a period of about 15 minutes. After this time themixture is stripped of benzene under reduced pressure to yield a solidproduct as the residue. The residue is then recrystallized to yield thedesired product the dimethyl acetal of3-[1-methyl-3-(5-methyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 4 Preparation ofTetrahydro-1-(5-methyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone

The dimethyl acetal of3-[1-methyl-3-(5-methyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde (15grams), water (400 ml) and hydrochloric acid (4 ml) are charged into aglass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux for aperiod of about 15 minutes. The reaction mixture is then filtered whilehot and the filtrate is cooled to form a precipitate. The precipitate isrecovered by filtration, is dried and is recrystallized to yield thedesired producttetrahydro-1-(5-methyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 5 Preparation ofTetrahydro-1-(5-methyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-methyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.1 mole), acetic anhydride (0.11 mole),toluenesulfonic acid (0.05 gram) and benzene (100 ml) are charged into aglass reaction vessel equipped with a mechanical stirrer andthermometer. The reaction mixture is heated on a steam bath withstirring for a period of about 2 hours. After this time the reactionmixture is cooled to room temperature and is stripped of solvent underreduced pressure leaving a residue. The residue is recrystallized toyield the desired producttetrahydro-1-(5-methyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone.

EXAMPLE 6 Preparation of 5-Methoxy-1,3,4-thiadiazol-2-yl IsocyanateDimer

A saturated solution of phosgene in ethyl acetate (100 ml) is chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-methoxy-2-amino-1,3,4-thiadiazole (40 grams) in ethylacetate (300 ml) is added to the reaction vessel and the resultingmixture is stirred for a period of about 16 hours, resulting in theformation of a precipitate. The reaction mixture is then purged withnitrogen gas to remove unreacted phosgene. The purged mixture is thenfiltered to recover the precipitate. The precipitate is thenrecrystallized to yield the desired product5-methoxy-1,3,4-thiadiazol-2-yl isocyanate dimer.

EXAMPLE 7 Preparation of the Dimethyl Acetal of3-Ethylaminopropionaldehyde

Ethylamine (2.0 mole), the dimethyl acetal of 3-bromopropionaldehyde(1.0 mole) and methanol (100 ml) are charged into a glass reactionvessel equipped with a mechanical stirrer, thermometer and refluxcondenser. The reaction mixture is heated at reflux, with stirring, fora period of about 5 hours. After this time the reaction mixture iscooled to room temperature and sodium hydroxide (20 grams) is added. Thereaction mixture is then stirred for an additional period of about 12hours. The reaction mixture is then filtered and the filtrate isdistilled under reduced pressure to yield the desired product thedimethyl acetal of 3-ethylaminopropionaldehyde.

EXAMPLE 8

Preparation of the Dimethyl Acetal of3-[1-(Ethyl-3-(5-methoxy-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-methoxy-1,3,4-thiadiazol-2-yl isocyanate dimer (0.05mole), the dimethyl acetal of 3-ethylaminopropionaldehyde (0.1 mole) andbenzene (60 ml) are charged into a glass reaction vessel equipped with amechanical stirrer and reflux condenser. The reaction mixture is heatedat reflux for a period of about 15 minutes. After this time the mixtureis stripped of benzene under reduced pressure to yield a solid productas the residue. The residue is then recrystallized to yield the desiredproduct the dimethyl acetal of3-[1-ethyl-3-(5-methoxy-1,3,4-thiadizol-2-yl)ureido]propionaldehyde.

EXAMPLE 9 Preparation ofTetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-ethyl-6-hydroxy-2(1H)-pyrimidinone

The dimethyl acetal of3-[1-ethyl-3-(5-methoxy-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde (15grams), water (400 ml) and hydrochloric acid (4 ml) are charged into aglass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux for aperiod of about 15 minutes. The reaction mixture is then filtered whilehot and the filtrate is cooled to form a precipitate. The precipitate isrecovered by filtration, is dried and is recrystallized to yield thedesired producttetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-ethyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 10 Preparation ofTetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-ethyl-6-propionyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-ethyl-6-hydroxy-2(1H)-pyrimidinone(0.1 mole), propionic anhydride (0.11 mole), toluenesulfonic acid (0.05gram) and benzene (100 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and thermometer. The reaction mixtureis heated on a steam bath with stirring for a period of about 2 hours.After this time the reaction mixture is cooled to room temperature andis stripped of solvent under reduced pressure leaving a residue. Theresidue is recrystallized to yield the desired producttetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-ethyl-6-propionlyoxy-2(1H)-pyrimidinone.

EXAMPLE 11 Preparation of 5-Methylthio-1,3,4-thiadiazol-2-yl IsocyanateDimer

A saturated solution of phosgene in ethyl acetate (100 ml) is chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-methylthio-2-amino-1,3,4-thiadiazole (45 grams) in ethylacetate (300 ml) is added to the reaction vessel and the resultingmixture is stirred for a period of about 16 hours, resulting in theformation of a precipitate. The reaction mixture is then purged withnitrogen gas to remove unreacted phosgene. The purged mixture is thenfiltered to cover the precipitate. The precipitate is thenrecrystallized to yield the desired product5-methylthio-1,3,4-thiadiazol-2-yl isocyanate dimer.

EXAMPLE 12 Preparation of the Dimethyl Acetal of3Propylaminopropionaldehyde

Propylamine (2.0 mole), the dimethyl acetal of 3-bromopropionaldehyde(1.0 mole) and methanol (100 ml) are charged into a glass reactionvessel equipped with a mechanical stirrer, thermometer and refluxcondenser. The reaction mixture is heated at reflux, with stirring, fora period of about 3 hours. After this time the reaction mixture iscooled to room temperature and sodium hydroxide (20 grams) is added. Thereaction mixture is then stirred for an additional period of about 6hours. The reaction mixture is then filtered and the filtrate isdistilled under reduced pressure to yield the desired product thedimethyl acetal of 3-propylaminopropionaldehyde.

EXAMPLE 13 Preparation of the Dimethyl Acetal of3-[1-Propyl-3-(5-methylthio-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-methylthio-1,3,4-thiadiazol-2-yl isocyanate dimer (0.05mole), the dimethyl acetal of 3-propylaminopropionaldehyde (0.1 mole)and benzene (60 ml) are charged into a glass reaction vessel equippedwith a mechanical stirrer and reflux condenser. The reaction mixture isheated at reflux for a period of about 15 minutes. After this time themixture is stripped of benzene under reduced pressure to yield a solidproduct as the residue. The residue is then recrystallized to yield thedesired product the dimethyl acetal of3-[1-propyl-3(5-methylthio-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 14 Preparation ofTetrahydro-1-(5-methylthio-1,3,4-thiadiazol-2-yl)-3-propyl-6-hydroxy2(1H)-pyrimidinone

The dimethyl acetal of3-[1-propyl-3-(5-methylthio-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde(15 grams), water (400 ml ) and hydrochloric acid (4 ml) are chargedinto a glass reaction vessel equipped with a mechanical stirrer,thermometer and reflux condenser. The reaction mixture is heated atreflux for a period of about 15 minutes. The reaction mixture is thenfiltered while hot and the filtrate is cooled to form a precipitate. Theprecipitate is recovered by filtration, is dried and is recrystallizedto yield the desired producttetrahydro-1-(5-methylthio-1,3,4-thiadiazol-2-yl)-3-propyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 15 Preparation ofTetrahydro-1-(5-methylthio-1,3,4-thiadiazol-2-yl)-3-propyl-6-butanoyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-methylthio-1,3,4-thiadiazol-2-yl)-3-propyl-6-hydroxy-2(1H)-pyrimidinone(0.1 mole), butanoic anhydride (0.11 mole), toluenesulfonic acid (0.05gram) and benzene (100 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and thermometer. The reaction mixtureis heated on a steam bath with stirring for a period of about 2 hours.After this time the reaction mixture is cooled to room temperature andis stripped of solvent under reduced pressure leaving a residue. Theresidue is recrystallized to yield the desired producttetrahydro-1-(5-methylthio-1,3,4-thiadiazol-2-yl)-3-propyl-6-butanoyloxy-2(1H)-pyrimidinone.

EXAMPLE 16 Preparation of 5-Methylsulfonyl-1,3,4-thiadiazol-2-ylIsocyanate Dimer

A saturated solution of phosgene in ethyl acetate (100 ml) is chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-methylsulfonyl-2-amino-1,3,4-thiadiazole (50 grams) in ethylacetate (300 ml) is added to the reaction vessel and the resultingmixture is stirred for a period of about 16 hours, resulting in theformation of a precipitate. The reaction mixture is then purged withnitrogen gas to remove unreacted phosgene. The purged mixture is thenfiltered to recover the precipitate. The precipitate is thenrecrystallized to yield the desired product5-methylsulfonyl-1,3,4-thiadiazol-2yl isocyanate dimer.

EXAMPLE 17 Preparation of the Dimethyl Acetal of3-Allylaminopropionaldehyde

Allylamine (1.0 mole), the dimethyl acetal of 3-bromopropionaldehyde(0.5 mole) and methanol (100 ml) are charged into a glass reactionvessel equipped with a mechanical stirrer, thermometer and refluxcondenser. The reaction mixture is heated at reflux, with stirring, fora period of about 8 hours. After this time the reaction mixture iscooled to room temperature and sodium hydroxide (20 grams) is added. Thereaction mixture is then stirred for an additional period of about 14hours. The reaction mixture is then filtered and the filtrate isdistilled under reduced pressure to yield the desired product thedimethyl acetal of 3-allylaminopropionaldehyde.

EXAMPLE 18 Preparation of the Dimethyl Acetal of3-[1-Allyl-3-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-methylsulfonyl-1,3,4-thiadiazol-2yl isocyanate dimer(0.05 mole), the dimethyl acetal of 3-allylaminopropionaldehyde (0.1mole) and benzene (60 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and reflux condenser. The reactionmixture is heated at reflux for a period of about 15 minutes. After thistime the mixture is stripped of benzene under reduced pressure to yielda solid product as the residue. The residue is then recrystallized toyield the desired product the dimethyl acetal of3-[1-allyl-3-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 19 Preparation ofTetrahydro-1-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-3-allyl-6-hydroxy-2-(1H)-pyrimidinone

The dimethyl acetal of3-[1-methyl-3-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde(15 grams), water (400 ml) and hydrochloric acid (4 ml) are charged intoa glass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux for aperiod of about 15 minutes. The reaction is then filtered while hot andthe filtrate is cooled to form a precipitate. The precipitate isrecovered by filtration, is dried and is recrystallized to yield thedesired producttetrahydro-1-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-3-allyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 20 Preparation ofTetrahydro-1-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-3-allyl-6-cyclohexylcarbonyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-methylsulfonyl-1,3,4-thiadiazol-2yl)-3-allyl-6-hydroxy-2(1H)-pyrimidinone(0.1 mole), cyclohexane carboxylic anhydride (0.11 mole),toluenesulfonic acid (0.05 gram) and benzene (100 ml) are charged into aglass reaction vessel equipped with a mechanical stirrer andthermometer. The reaction mixture is heated on a stream bath withstirring for a period of about 2 hours. After this time the reactionmixture is cooled to room temperature and is stripped of solvent underreduced pressure leaving a residue. The residue is recrystallized toyield the desired producttetrahydro-1-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-3-allyl-6-cyclohexylcarbonyloxy-2(1H)-pyrimidinone.

EXAMPLE 21 Preparation of 5-Methylsulfinyl-1,3,4-thiadiazol-2-ylIsocyanate Dimer

A saturated solution of phosgene in ethyl acetate (100 ml) is chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-methylsulfinyl-2-amino-1,3,4-thiadiazole (50 grams) in ethylacetate (300 ml) is added to the reaction vessel and the resultingmixture is stirred for a period of about 16 hours, resulting in theformation of a precipitate. The reaction mixture is then purged withnitrogen gas to remove unreacted phosgene. The purged mixture is thenfiltered to recover the precipitate. The precipitate is thenrecrystallized to yield the desired product5-methylsulfinyl-1,3,4-thiadiazol-2-yl isocyanate dimer.

EXAMPLE 22 Preparation of the Dimethyl Acetal of3-Propargylaminopropionaldehyde

Propargylamine (2.0 mole), the dimethyl acetal of 3-bromopropionaldehyde(1.0 mole) and methanol (100 ml) are charged into a glass reactionvessel equipped with a mechanical stirrer, thermometer and refluxcondenser. The reaction mixture is heated at reflux, with stirring, fora period of about 6 hours. After this time the reaction mixture iscooled to room temperature and sodium hydroxide (20 grams) is added. Thereaction mixture is then stirred for an additional period of about 18hours. The reaction mixture is then filtered and the filtrate isdistilled under reduced pressure to yield the desired product thedimethyl acetal of 3-propargylaminopropionaldehyde.

EXAMPLE 23 Preparation of the Dimethyl Acetal of3-[1-Propargyl-3-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-methylsulfinyl-1,3,4-thiadiazol-2-yl isocyanate dimer(0.05 mole), the dimethyl acetal of 3-propargylaminopropionaldehyde (0.1mole) and benzene (60 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and reflux condenser. The reactionmixture is heated at reflux for a period of about 15 minutes. After thistime the mixture is stripped of benzene under reduced pressure to yielda solid product as the residue. The residue is then recrystallized toyield the desired product the dimethyl acetal of3-[1-propargyl-3-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 24 Preparation ofTetrahydro-1-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-3-propargyl-6-hydroxy-2(1H)-pyrimidinone

The dimethyl acetal of3-[1-propargyl-3-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde(15 grams), water (400 ml) and hydrochloric acid (4ml) are charged intoa glass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux for aperiod of about 15 minutes. The reaction mixture is then filtered whilehot and the filtrate is cooled to form a precipitate. The precipitate isrecovered by filtration, is dried and is recrystallized to yield thedesired producttetrahydro-1-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-3-propargyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 25 Preparation ofTetrahydro-1-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-3-propargyl-6-benzoyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-3-propargyl-6-hydroxy-2(1H)-pyrimidinone(0.1 mole), benzoic anhydride (0.11 mole), toluenesulfonic acid (0.05gram) and benzene (100 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and thermometer. The reaction mixtureis heated on a steam bath with stirring for a period of about 2 hours.After this time the reaction mixture is cooled to room temperature andis stripped of solvent under reduced pressure leaving a residue. Theresidue is recrystallized to yield the desired producttetrahydro-1-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-3-propargyl-6-benzoyloxy-2(1H)-pyrimidinone.

EXAMPLE 26 Preparation of 5-Trifluoromethyl-1,3,4-thiadiazol-2-ylIsocyanate Dimer

A saturated solution of phosgene in ethyl acetate (100 ml) was chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-trifluoromethyl-2-amino-1,3,4-thiadiazole (45grams) in ethylacetate (300 ml) was added to the reaction vessel and the resultingmixture was stirred for a period of about 16 hours resulting in theformation of a precipitate. The reaction mixture was then purged withnitrogen gas to remove unreacted phosgene. The purged mixture wasfiltered to recover 48 grams of a white solid. This solid wasrecrystallized from dimethyl formamide to yield the desired product5-trifluoromethyl-1,3,4-thiadiazol-2yl isocyanate dimer.

EXAMPLE 27 Preparation of the Dimethyl Acetal of3-[1-Methyl-3-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-trifluoromethyl-1,3,4-thiadiazol-2yl isocyanate dimer(9.5 grams), the dimethyl acetal of 3-methylaminopropionaldehyde (5.8grams) and benzene (60 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and reflux condenser. The reactionmixture is heated at reflux for a period of about 15 minutes. After thistime the mixture is stripped of benzene under reduced pressure to yielda solid product as the residue. This product is recrystallized to yieldthe desired product the dimethyl acetal of3-[1-methyl-3-trifluoromethyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 28 Preparation ofTetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone

The dimethyl acetal of3-[1-methyl-3-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde(15 grams), water (400 ml) and hydrochloric acid (4 ml) are charged intoa glass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux for aperiod of about 15 minutes. The reaction mixture is then filtered whilehot and the filtrate is cooled resulting in the formation of aprecipitate. The precipitate is recovered by filtration, is dried and isrecrystallized to yield the desired producttetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 29 Preparation ofTetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone(0.1mole), acetic anhydride (0.11 mole), toluenesulfonic acid (0.05gram) and benzene (100 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer and thermometer. The reaction mixtureis heated on a steam bath with stirring for a period of about 2 hours.After this time the reaction mixture is cooled to room temperature andis stripped of solvent under reduced pressure leaving a residue. Theresidue is recrystallized to yield the desired producttetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone.

EXAMPLE 30 Preparation of 5-t-Butyl-1,3,4-thiadiazol-2-yl IsocyanateDimer

A saturated solution of phosgene in ethyl acetate (100 ml) was chargedinto a glass reaction vessel equipped with a mechanical stirrer. Aslurry of 5-t-butyl-2-amino-1,3,4-thiadiazole (10 grams) in ethylacetate (300 ml) was added to the reaction vessel and the resultingmixture was stirred for a period of about 16 hours resulting in theformation of a precipitate. The reaction mixture was then purged withnitrogen gas to remove unreacted phosgene. The purged mixture was thenfiltered to recover the desired product 5-t-butyl-1,3,4-thiadiazol-2-ylisocyanate dimer as a solid having a melting point of 261° to 263° C.

EXAMPLE 31 Preparation of the Dimethyl Acetal of3-[1-Methyl-3-(5-t-butyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-t-buty-1,3,4-thiadiazol-2-yl isocyanate dimer (6 grams),the dimethyl acetal of 3-methylaminopropionaldehyde (4.0 grams) andbenzene (50 ml) are charged into a glass reaction flask equipped with amechanical stirrer and reflux condenser. The reaction mixture is heatedat reflux, with stirring, for a period of about 5 minutes. After thistime the reaction mixture is stripped of benzene to yield a residue. Theresidue is then recrystallized to yield the desired product the dimethylacetal of3-[1-methyl-(5-t-butyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 32 Preparation ofTetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone

The dimethyl acetal of3-[1-methyl-3-(5t-butyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde (16grams), concentrated hydrochloric acid (10 ml) and water (500 ml) arecharged into a glass reaction vessel equipped with a mechanical stirrer,thermometer and reflux condenser. The reaction mixture is heated atreflux for a period of about 15 minutes. The reaction mixture isfiltered while hot and the filtrate is then cooled, resulting in theformation of a precipitate. The precipitate is recovered by filtration,dried and is recrystallized to yield the desired producttetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 33 Preparation ofTetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.1 mole), acetic anhydride (0.11 mole),toluenesulfonic acid (0.05 gram) and benzene (100 ml) are charged into aglass reaction vessel equipped with a mechanical stirrer andthermometer. The reaction mixture is heated on a steam bath withstirring for a period of about 2 hours. After this time the reactionmixture is cooled to room temperature and is stripped of solvent underreduced pressure leaving a residue. The residue is recrystallized toyield the desired producttetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone.

EXAMPLE 34 Preparation of the Diethyl Acetal of3-But-3-enylaminopropionaldehyde

But-3-enylamine (1.0 mole), the diethyl acetal of 3-bromopropionaldehyde(1.0 mole) and methanol (100 ml) are charged into a glass reactionvessel equipped with a mechanical stirrer, thermometer and refluxcondenser. The reaction mixture is heated at reflux with stirring for aperiod of about 6 hours. After this time the reaction mixture is cooledto room temperature and sodium hydroxide (20 grams) is added. Thereaction mixture is then stirred for an additional period of about 16hours. The mixture is then filtered and the filtrate is distilled toyield the desired product the diethyl acetal of3-but-3-enylaminopropionaldehyde.

EXAMPLE 35 Preparation of the Diethyl Acetal of3-[1-But-3-enyl-3-(5-methoxy-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-methoxy-1,3,4-thiadiazol-2-yl isocyanate dimer (0.05mole), the diethyl acetyl of 3-but-3-enylaminopropionaldehyde (0.1 mole)and benzene (60 ml) are charged into a glass reaction vessel equippedwith a mechanical stirrer and reflux condenser. The reaction mixture isheated at reflux for a period of about 15 minutes. After this time themixture is stripped of benzene under reduced pressure to yield thedesired product the diethyl acetal of3-[1-but-3-enyl-3-(5-methoxy-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde.

EXAMPLE 36 Preparation ofTetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-but-3-enyl-6-hydroxy-2(1H)-pyrimidinone

The diethyl acetal of 3-[1-but-3-enyl-3-(5-methoxy-1,3,4-thiadiazol-2-yl)ureido] propionaldehyde (15 grams), water (400 ml) andhydrochloric acid (4 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflex condenser.The reaction mixture is heated at reflux for a period of about 15minutes. The reaction mixture is then filtered while hot and thefiltrate is cooled to form a precipitate. The precipitate is recoveredby filtration, is dried and is recrystallized to yield the desiredproduct tetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-but-3-enyl-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 37 Preparation of Tetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-but-3-enyl-6-(4-chlorobenzoyloxy)-2(1H)-pyrimidinone

Tetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-but-3-enyl-6-hydroxy-2(1H)-pyrimidinone (0.1 mole), 4 -chlorobenzoicanhydride (0.11 mole), toluenesulfonic acid (0.05 gram) and benzene (100ml) are charged into a glass reaction vessel equipped with a mechanicalstirrer and thermometer. The reaction mixture is heated on a steam bathwith stirring for a period of about 2 hours. After this time thereaction mixture is cooled to room temperature and is stripped ofsolvent under reduced pressure leaving a residue. The residue isrecrystallized to yield the desired producttetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-but-3-enyl-6-(4-chlorobenzoyloxy)-2(1H)-pyrimidinone.

EXAMPLE 38 Preparation of the Diethyl Acetal of3-(1,1-Dimethylprop-2-ynylamino)propionaldehyde

1,1-Dimethylprop-2-ynylamine (1.0 mole), the diethyl acetal of3-bromopropionaldehyde (1.0 mole) and methanol (100 ml) are charged intoa glass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux withstirring for a period of about 6 hours. After this time the reactionmixture is cooled to room temperature and sodium hydroxide (20 grams) isadded. The reaction mixture is then stirred for an additional period ofabout 16 hours. The mixture is then filtered and the filtrate isdistilled to yield the desired product the diethyl acetal of3-(1,1-dimethylprop- 2-ynylamino)propionaldehyde.

EXAMPLE 39 Preparation of the Diethyl Acetal of3-[1,1-Dimethylprop-2-ynyl)-3-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)ureido]propionaldehyde

A mixture of 5-trifluoromethyl-1,3,4-thiadiazol- 2-yl isocyanate dimer(0.05 mole), the diethyl acetal of3-(1,1-dimethylprop-2-ynylamino)propionaldehyde (0.1 mole) and benzene(60 ml) are charged into a glass reaction vessel equipped with amechanical stirrer and reflux condenser. The reaction mixture is heatedat reflux for a period of about 15 minutes. After this time the mixtureis stripped of benzene under reduced pressure to yield a solid productas the residue. The residue is then recrystallized to yield the desiredproduct the diethyl acetal of 3-[1-(1,1-dimethylprop-2-ynyl)-3-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-ureido]propionaldehyde.

EXAMPLE 40 Preparation ofTetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-(1,1-dimethylprop-2-ynyl)-6-hydroxy-2(1H)-pyrimidinone

The diethyl acetal of 3-[1,1-dimethylprop-2-ynyl)-3-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)ureido]-propionaldehyde(15 grams), water (400 ml) and hydrochloric acid (4 ml) are charged intoa glass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. The reaction mixture is heated at reflux for aperiod of about 15 minutes. The reaction mixture is then filtered whilehot and the filtrate is cooled to form a precipitate. The precipitate isrecovered by filtration, is dried and is recrystallized to yield thedesired product tetrahydro-1 -(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-(1,1-dimethylprop-2-ynyl)-6-hydroxy-2(1H)-pyrimidinone.

EXAMPLE 41 Preparation of Tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-(1,1-dimethylprop-2-ynyl-6-(2-methylbenzoyloxy)-2(1H)-pyrimidinone

Tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-(1,1-dimethylprop-2-ynyl)-6-hydroxy-2(1H)-pyrimidinone (0.05mole), triethylamine (0.06 mole) and benzene (50 ml) are charged into aglass reaction vessel equipped with a mechanical stirrer, thermometerand reflux condenser. 2-Methylbenzoyl chloride (0.05 mole) is then addeddropwise with stirring. After the addition is completed, the reactionmixture is heated at reflux with continued stirring for a period ofabout 30 minutes. After this time the reaction mixture is filtered andthe filtrate is stripped of solvent under reduced pressure to yield asolid residue. The residue is recrystallized to yield the desiredproduct tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-(1,1-dimethylprop-2-ynyl)-6-(2-methylbenzoyloxy)-2(1H)-pyrimidinone.

EXAMPLE 42 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(2-methyl-4-chlorobenzoyloxy)-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.2-Methyl-4-chlorobenzoyl chloride (0.05 mole) is then added dropwisewith stirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield a solidresidue. The residue is recrystallized to yield the desired producttetrahydro- 1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(2-methyl-4-chlorobenzoyloxy)-2(1H)-pyrimidinone.

EXAMPLE 43 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-methoxybenzoyloxy)-2(1H)-pyrimidione

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.4-Methoxybenzoyl chloride (0.05 mole) is then added dropwise withstirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield thedesired product tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-methoxybenzoyloxy)-2(1 H)-pyrimidinone.

EXAMPLE 44 Preparation of Tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-chloromethyl-6-hexanoyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-chloromethyl-6-hydroxy-2(1H)-pyrimidinone(0.05 mole), triethylamine (0.06 mole) and benzene (50 ml) are chargedinto a glass reaction vessel equipped with a mechanical stirrer,thermometer and reflux condenser. Hexanoyl chloride (0.05 mole) is thenadded dropwise with stirring. After the addition is completed, thereaction mixture is heated at reflux with continued stirring for aperiod of about 30 minutes. After this time the reaction mixture isfiltered and the filtrate is stripped of solvent under reduced pressureto yield a solid residue. The residue is recrystallized to yield thedesired product tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-chloromethyl-6-hexanoyloxy-2(1H)-pyrimidinone.

EXAMPLE 45 Preparation ofTetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-trifluoromethylbenzoyloxy)-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06 mole) andbenzene (50 ml) are charged into a glass reaction vessel equipped with amechanical stirrer, thermometer and reflux condenser.4-Trifluoromethylbenzoyl chloride (0.05 mole) is then added dropwisewith stirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield a solidresidue. The residue is recrystallized to yield the desired producttetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-trifluoromethylbenzoyloxy)-2(1H)-pyrimidinone.

EXAMPLE 46 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[α-(4-cyanophenyl)acetyloxy]-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06 mole) andbenzene (50 ml) are charged into a glass reaction vessel equipped with amechanical stirrer, thermometer and reflux condenser.α-(4-Cyanophenyl)acetyl chloride (0.05 mole) is then added dropwise withstirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield thedesired product tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[α-(4-cyanophenyl)acetyloxy]-2(1H)-pyrimidinone as theresidue.

EXAMPLE 47 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[α-(3,5-dinitrophenyl)acetyloxy]-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.α-(3,5-Dinitrophenyl)acetyl chloride (0.05 mole) is then added dropwisewith stirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield thedesired product tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[α-(3,5-dinitrophenyl)acetyloxy] -2 (1H)-pyrimidinone as the residue.

EXAMPLE 48 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3 -methyl-6-[ β-(4-chlorophenyl)propionyloxy]-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.β-(4-Chlorophenyl)propionyl chloride (0.05 mole) is then added dropwisewith stirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield thedesired product tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[β-(4-chlorophenyl)propionyloxy] -2(1H)-pyrimidinone as the residue.

EXAMPLE 49 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[γ-(3-bromophenyl)butanoyloxy]-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.γ-(3-Bromophenyl)butanoyl chloride (0.05 mole) is then added dropwisewith stirring. After the addition is completed, the reaction mixture isheated at reflux with continued stirring for a period of about 30minutes. After this time the reaction mixture is filtered and thefiltrate is stripped of solvent under reduced pressure to yield thedesired product tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-[γ-(3-bromophenyl)-butanoyloxy]-2(1H)-pyrimidinone as the residue.

EXAMPLE 50 Preparation ofTetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-chloroacetyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine(0.06 mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.Chloroacetyl chloride (0.05 mole) is then added dropwise with stirring.After the addition is completed, the reaction mixture is heated atreflux with continued stirring for a period of about 30 minutes. Afterthis time the reaction mixture is filtered and the filtrate is strippedof solvent under reduced pressure to yield the desired producttetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-chloroacetyloxy- 2(1H)-pyrimidinone asthe residue.

EXAMPLE 51 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-methoxyacetyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.Methoxyacetyl chloride (0.05 mole) is then added dropwise with stirring.After the addition is completed, the reaction mixture is heated atreflux with continued stirring for a period of about 30 minutes. Afterthis time the reaction mixture is filtered and the filtrate is strippedof solvent under reduced pressure to yield the desired producttetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-methoxyacetyloxy-2(1H)-pyrimidinone as the residue.

EXAMPLE 52 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-propynoyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.Propynoyl chloride (0.05 mole) is then added dropwise with stirring.After the addition is completed, the reaction mixture is heated atreflux with continued stirring for a period of about 30 minutes. Afterthis time the reaction mixture is filtered and the filtrate is strippedof solvent under reduced pressure to yield the desired producttetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-propynoyloxy-2(1H)-pyrimidinone as the residue.

EXAMPLE 53 Preparation of Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acryloyloxy-2(1H)-pyrimidinone

Tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hydroxy-2(1H)-pyrimidinone (0.05 mole), triethylamine (0.06mole) and benzene (50 ml) are charged into a glass reaction vesselequipped with a mechanical stirrer, thermometer and reflux condenser.Acryloyl chloride (0.05 mole) is then added dropwise with stirring.After the addition is completed, the reaction mixture is heated atreflux with continued stirring for a period of about 30 minutes. Afterthis time the reaction mixture is filtered and the filtrate is strippedof solvent under reduced pressure to yield the desired producttetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acryloyloxy-2(1H)-pyrimidinone as the residue.

Additional compounds within the scope of this invention which can beprepared by the procedures of the foregoing examples aretetrahydro-1-(5-ethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acryloyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-propyl-1,3,4-thiadiazol-2-yl)-3butyl-6-but-3-enoyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-butyl-1,3,4-thiadiazol-2-yl)-3-pentyl-6-pent-3-enoyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-pentyl-1,3,4-thiadiazol-2-yl)-3-hexyl-6-hex-4-enoyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-hexyl-1,3,4-thiadiazol-2-yl)-3-pent-3-enyl-6-pentanoyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-cyclopropyl-1,3,4-thiadiazol-2-yl)-3-hex-4-enyl-6-hexanoyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-cyclobutyl-1,3,4-thiadiazol-2-yl)-3-bromomethyl-6-butanoyloxy- 2(1H)-pyrimidinone,tetrahydro-1-(5-cyclopentyl-1,3,4-thiadiazol-2-yl)-3-trichloromethyl-6-chloroacetyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-cyclohexyl- -thiadiazol-2-yl)-3-β-chlorohexyl-6-bromoacetyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-cycloheptyl-1,3,4-thiadiazol-2-yl)-3-β-bromoethyl-6-β-chlorobutanoyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-allyl-1,3,4-thiadiazol-2-yl)-3-(1,1-diethylprop-2-ynyl)-6-cyclopropylcarbonyloxy-2(1H)-pyrimidinone,tetrahydro-1-((5-but-3-enyl-1,3,4-thiadiazol-2yl)-3-(1,1-dipropylprop-2ynyl)-6-cyclobutylcarbonyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-pent-4-enyl-1,3,4-thiadiazol-2yl)-3-methyl-6-cyclopentylcarbonyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-hex-4-enyl-1,3,4-thiadiazol-2yl)-3-methyl-6-cyclohexylcarbonyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-chloromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-cycloheptylcarbonyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-bromomethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-methylthiobenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-trichloromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-ethylthiobenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-β-chloroethyl- 1,3,4-thiadiazol-2yl)-3-methyl-6-(3-propylthiobenzoyloxy)- 2(1H)-pyrimidinone, tetrahydro-1-(5-β-bromoethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6(3-hexylthiobenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-ω-chlorohexyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(3,4,5-trichlorobenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-ethoxy-1,3,4-thiadiazol-2-yl)-3-methyl-6-(3-ethylbenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-propoxy-1,3,4-thiadiazol-2yl)-3-methyl-6-(4-propylbenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-butoxy-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-butylbenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-hexyloxy-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-hexylbenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-ethylthio-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-bromobenzoyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-propylthio-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-iodobenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-hexylthio-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-fluorobenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-ethylsulfonyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(2-ethoxybenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-propylsulfonyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(3-propoxybenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-butylsulfonyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-hexyloxybenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-hexylsulfonyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(3-chloromethylbenzoyloxy)-2(1H)-pyrimidinone, tetrahydro-1-(5-ethylsulfinyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-trifluoromethylbenzoyloxy)- 2(1H)-pyrimidinone,tetrahydro-1-(5-propysulfinyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-(4-β-bromoethylbenzoyloxy)-2(1H)-pyrimidinone,tetrahydro-1-(5-hexylsulfinyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6bromoacetyloxy-2(1H)-pyrimidinone, tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2yl)-3-methyl-6-β-chloropropanoyl- 2(1H)-pyrimidinone,tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-γ-chlorobutanoyl-2(1H)-pyrimidinone,tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2yl)-3-methyl-6-β-bromopentanoyl-2(1H)-pyrimidinone,tetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-ω-chlorohexanoyl-2(1H)-pyrimidinone,tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-but-3-enoyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-pent-4-enoyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hex-4-enoyloxy-2(1H)-pyrimidinone,tetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-but-3-ynoyloxy-2(1H)-pyrimidione,tetrahydro-1-(5-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-hex-4-ynoyloxy-2(1H)-pyrimidinone and the like.

For practical use as herbicides the compounds of this invention aregenerally incorporated into herbicidal compositions which comprise aninert carrier and a herbicidally toxic amount of such a compound. Suchherbicidal compositions, which can also be called formulations, enablethe active compound to be applied conveniently to the site of the weedinfestation in any desired quantity. These compositions can be solidssuch as dusts, granules, or wettable powders; or they can be liquidssuch as solutions, aerosols, or emulsifiable concentrates.

For example, dusts can be prepared by grinding and blending the activecompound with a solid inert carrier such as the talcs, clays, silicas,pyrophyllite, and the like. Granular formulations can be prepared byimpregnating the compound, usually dissolved in a suitable solvent, ontoand into granulated carriers such as the attapulgites or thevermiculites, usually of a particle size range of from about 0.3 to 1.5mm. Wettable powders, which can be dispersed in water or oil to anydesired concentration of the active compound, can be prepared byincorporating wetting agents into concentrated dust compositions.

In some cases the active compounds are sufficiently soluble in commonorganic solvents such as kerosene or xylene so that they can be useddirectly as solutions in these solvents. Frequently, solutions ofherbicides can be dispersed under super-atmospheric pressure asaerosols. However, preferred liquid herbicidal compositions areemulsifiable concentrates, which comprise an active compound accordingto this invention and as the inert carrier, a solvent and an emulsifier.Such emulsifiable concentrates can be extended with water and/or oil toany desired concentration of active compound for application as spraysto the site of the weed infestation. The emulsifiers most commonly usedin these concentrates are nonionic or mixtures of nonionic with anionicsurface-active agents. With the use of some emulsifier systems aninverted emulsion (water in oil) can be prepared for direct applicationto weed infestations.

A typical herbicidal composition according to this invention isillustrated by the following example, in which the quantities are inparts by weight.

EXAMPLE 46 Preparation of a Dust

    ______________________________________                                        Product of Example 5    10                                                    Powdered Talc           90                                                    ______________________________________                                    

The above ingredients are mixed in a mechanical grinder-blender and areground until a homogeneous, free-flowing dust of the desired particlesize is obtained. This dust is suitable for direct application to thesite of the weed infestation.

The compounds of this invention can be applied as herbicides in anymanner recognized by the art. One method for the control of weedscomprises contacting the locus of said weeds with a herbicidalcomposition comprising an inert carrier and as an essential activeingredient, in a quantity which is herbicidally toxic to said weeds, acompound of the present invention. The concentration of the newcompounds of this invention in the herbicidal compositions will varygreatly with the type of formulation and the purpose for which it isdesigned, but generally the herbicidal compositions will comprise fromabout 0.05 to about 95 percent by weight of the active compounds of thisinvention. In a preferred embodiment of this invention, the herbicidalcompositions will comprise from about 5 to about 75 percent by weight ofthe active compound. The compositions can also comprise such additionalsubstances as other pesticides, such as insecticides, nematocides,fungicides, and the like; stabilizers, spreaders, deactivators,adhesivies, stickers, fertilizers, activators, synergists, and the like.

The compounds of the present invention are also useful when combinedwith other herbicides and/or defoliants, dessicants, growth inhibitors,and the like in the herbicidal compositions heretofore described. Theseother materials can comprise from about 5% to about 95% of the activeingredients in the herbicidal compositions. Use of combinations of theseother herbicides and/or defoliants, dessicants, etc. with the compoundsof the present invention provide herbicidal compositions which are moreeffective in controlling weeds and often provide results unattainablewith separate compositions of the individual herbicides. The otherherbicides, defoliants, dessicants and plant growth inhibitors, withwhich the compounds of this invention can be used in the herbicidalcompositions to control weeds, can include chlorophenoxy herbicides suchas 2,4-D, 2,4,5-T, MCPA, MCPB, 4(2,4-DB), 2,4-DEB, 4-CPB, 4-CPA, 4-CPP,2,4,5-TB, 2,4,5-TES, 3,4-DA, silvex and the like; carbamate herbicidessuch as IPC, CIPC, swep, barban, BCPC, CEPC, CPPC, and the like;thiocarbamate and dithiocarbamate herbicides such as CDEC, methamsodium, EPTC, diallate, PEBC, perbulate, vernolate and the like;substituted urea herbicides such as norea, siduron, dichloral urea,chloroxuron, cycluron, fenuron, monuron, monuron TCA, diuron, linuron,monolinuron, neburon, buturon, trimeturon and the like; symmetricaltriazine herbicides such as simazine, chlorazine, atraone, desmetryne,norazine, ipazine, prometryn, atrazine, trietazine, simetone, prometone,propazine, ametryne and the like; chloroacetamide herbicides such asalpha-chloro-N,N-dimethylacetamide, CDEA, CDAA,alpha-chloro-N-isopropylacetamide, 2-chloro-N-isopropylacetanilide,4-(chloroacetyl)morpholine, 1-(chloroacetyl)piperidine and the like;chlorinated aliphatic acid herbicides such as TCA, dalapon,2,3-dichloropropionic acid, 2,2,3-TPA and the like; chlorinated benzoicacid and phenylacetic acid herbicides such as 2,3,6-TBA, 2,3,5,6-TBA,dicamba, tricamba, amiben, fenac, PBA,2-methoxy-3,6-dichlorophenylacetic acid,3-methoxy-2,6-dichlorophenylacetic acid,2-methoxy-3,5,6-trichlorophenylacetic acid, 2,4-dichloro-3-nitrobenzoicacid and the like; and such compounds as aminotriazole, maleichydrazide, phenyl mercuric acetate, endothal, biuret, technicalchlordane, dimethyl 2,3,5,6-tetrachloroterephthalate, diquat, erbon,DNC, DNBP, dichlobenil, DPA, diphenamid, dipropalin, trifluralin, solan,dicryl, merphos, DMPA, DSMA, MSMA, potassium azide, acrolein, benefin,bensulide, AMS, bromacil,2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione,bromoxynil, cacodylic acid, CMA, CPMF, cypromid, DCB, DCPA, dichlone,diphenatril, DMTT, DNAP, EBEP, EXD, HCA, ioxynil, IPX, isocil, potassiumcyanate, MAA, MAMA, MCPES, MCPP, MH, molinate, NPA, OCH, paraquat, PCP,picloram, DPA, PCA, pyrichlor, sesone, terbacil, terbutol, TCBA,brominil, CP-50144, H-176-1, H-732, M-2901, planavin, sodiumtetraborate, calcium cyanamid, DEF, ethyl xanthogen disulfide, sindone,sindone B, propanil and the like. Such herbicides can also be used inthe methods and compositions of this invention in the form of theirsalts, esters, amides, and other derivatives whenever applicable to theparticular parent compounds.

Weeds are undesirable plants growing where they are not wanted, havingno economic value, and interfering with the production of cultivatedcrops, with the growing of ornamental plants, or with the welfare oflivestock. Many types of weeds are known, including annuals such aspigweed, lambsquarters, foxtail, crabgrass, wild mustard, fieldpennycress, ryegrass, goose grass, chickweed, wild oats, velvet-leaf,purslane, barnyardgrass, smartweed, knotweed, cocklebur, wild buckwheat,kochia, medic, corn cockle, ragweed, sow-thistle, coffeeweed, croton,cuphea, dodder, fumitory, groundsel, hemp nettle, knawel, spurge,spurry, emex, jungle rice, pondweed, dog fennel, carpetweed,morningglory, bedstraw, ducksalad, naiad, cheatgrass, fall panicum,jimsonweed, witchgrass, switchgrass, watergrass, teaweed, wild turnipand sprangletop; biennials such as wild carrot, matricaria, wild barley,campion, chamomile, burdock, mullein, roundleaved mallow, bull thistle,hounds-tongue, moth mullein and purple star thistle; or perennials suchas white cockle, perennial ryegrass, quackgrass, Johnsongrass, Canadathistle, hedge bindweed, Bermuda grass, sheep sorrel, curly dock,nutgrass, field chickweed, dandelion, campanula, field bindweed, Russianknapweed, mesquite, toadflax, yarrow, aster, gromwell, horsetail,ironweed, sesbania, bulrush, cattail, winter-cress, horsenettle,nutsedge, milkweed and sicklepod.

Similarly, such weeds can be classified as broadleaf or grassy weeds. Itis economically desirable to control the growth of such weeds withoutdamaging beneficial plants or livestock.

The new compounds of this invention are particularly valuable for weedcontrol because they are toxic to many species and groups of weeds whilethey are relatively non-toxic to many beneficial plants. The exactamount of compound required will depend on a variety of factors,including the hardiness of the particular weed species, weather, type ofsoil, method of application, the kind of beneficial plants in the samearea and the like. Thus, while the application of up to only about oneor two ounces of active compound per acre may be sufficient for goodcontrol of a light infestation of weeds growing under adverseconditions, the application of ten pounds or more of an active compoundper acre may be required for good control of a dense infestation ofhardy perennial weeds growing under favorable conditions.

The herbicidal toxicity of the new compounds of this invention can beillustrated by many of the established testing techniques known to theart, such as pre- and post-emergence testing.

The herbicidal activity of the compounds of this invention wasdemonstrated by experiments carried out for the pre-emergence control ofa variety of weeds. In these experiments small plastic greenhouse potsfilled with dry soil were seeded with the various weed seeds.Twenty-four hours or less after seeding the pots were sprayed with wateruntil the soil was wet and the test compound formulated as an aqueousemulsion of an acetone solution containing emulsifiers was sprayed atthe indicated concentration on the surface of the soil.

After spraying, the soil containers were placed in the greenhouse andprovided with supplementary heat as required and daily or more frequentwatering. The plants were maintained under these conditions for a periodof 21 days, at which time the condition of the plants and the degree ofinjury to the plants was rated on a scale of from 0 to 10, as follows: 0= no injury, 1, 2 = slight injury, 3, 4 = moderate injury, 5, 6 =moderately severe injury, 7, 8, 9 = severe injury and 10 = death. Theeffectiveness of this compound is demonstrated by the data in Table I.

The herbicidal activity of the compounds of this invention was alsodemonstrated by experiments carried out for the post-emergence controlof a variety of weeds. In these experiments the compound to be testedwas formulated as an aqueous emulsion and sprayed at the indicateddosage on the foliage of the weeds that had attained a prescribed size.After spraying, the plants were placed in a greenhouse and watered dailyor more frequently. Water was not applied to the foliage of the treatedplants. The severity of the injury was determined 14 days aftertreatment and was rated on the scale of from 0 to 10 heretoforedescribed. The effectiveness of this compound is demonstrated by thedata in Table I.

                  TABLE I                                                         ______________________________________                                        INJURY RATING                                                                           Product of Example 29                                                         at 10 lbs. per acre                                                 Weed Species                                                                              Pre-emergence Post-emergence                                      ______________________________________                                        Yellow Nutsedge                                                                            8             8                                                  Wild Oats   10            10                                                  Jimsonweed  10            10                                                  Velvetleaf  10            --                                                  Johnsongrass                                                                               8            10                                                  Pigweed      7            10                                                  Mustard     10            10                                                  Yellow Foxtail                                                                            10            10                                                  Barnyardgrass                                                                             10            10                                                  Crabgrass    9            10                                                  Cheatgrass  10            --                                                  Morningglory                                                                              10            10                                                  Bindweed    --             9                                                  ______________________________________                                    

I claim:
 1. A compound of the formula ##STR17## wherein R¹ is selectedfrom the group consisting of lower alkyl, lower alkenyl, lowerchloroalkyl, lower bromoalkyl, trifluoromethyl, lower alkoxy, loweralkylthio, lower alkylsulfonyl and lower alkylsulfinyl; R² is selectedfrom the group consisting of lower alkyl, lower alkenyl, lowerchloroalkyl, lower bromalkyl and ##STR18## wherein R³ and R⁴ are eachselected from the group consisting of hydrogen and lower alkyl; and R⁵is selected from the group consisting of lower alkyl, lower chloroalkyl,lower bromoalkyl, lower alkenyl, lower alkynyl, lower alkoxyalkyl,cycloalkyl of from 3 to 7 carbon atoms, and ##STR19## wherein X isselected from the group consisting of lower alkyl, halogen, lowerhaloalkyl, nitro, cyano and lower alkoxy and m and n are each integersfrom 0 to
 3. 2. The compound of claim 1, which istetrahydro-1-(5-methyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone.3. The compound of claim 1, which istetrahydro-1-(5-methoxy-1,3,4-thiadiazol-2-yl)-3-ethyl-6-propionyloxy-2(1H)-pyrimidinone.4. The compound of claim 1, which istetrahydro-1-(5-methylthio-1,3,4-thiadiazol-2-yl)-3-propyl-6-butanoyloxy-2(1H)-pyrimidinone.5. The compound of claim 1, which istetrahydro-1-(5-methylsulfonyl-1,3,4-thiadiazol-2-yl)-3-allyl-6-cyclohexylcarbonyloxy-2(1H)-pyrimidinone.6. the compound of claim 1, which istetrahydro-1-(5-methylsulfinyl-1,3,4-thiadiazol-2-yl)-3-propargyl-6-benzoyloxy-2(1H)-pyrimidinone.7. The compound of claim 1, which istetrahydro-1-(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone.8. The compound of claim 1, which istetrahydro-1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-methyl-6-acetyloxy-2(1H)-pyrimidinone.9. A herbicidal composition comprising an inert carrier and, as anessential active ingredient, in a quantity toxic to weeds, a compound ofclaim
 1. 10. A method of controlling weeds which comprises contactingsaid weeds with a herbicidal composition comprising an inert carrierand, as an essential active ingredient, in a quantity toxic to weeds, acompound of claim 1.